This is the PIE base for God in the The American Heritage Dictionary of Indo-European Roots, meaning ‘to call, invoke’, also root of giddy ‘possessed by a god’, from *ĝhau-, the root/lemma in Pokorny. Scholars have proposed Pokorny’s ĝheu- ‘to pour a libation, offer a sacrifice’ as an alternative base, the root of gush, fushion, and diffuse.
The OED says, “Either of these conjectures is fairly plausible, as they both yield a sense practically coincident with the most obvious definition deducible from the actual use of the word, ‘an object of worship’.” Much more information in the etymological dictionaries.
[Pokorny *ĝhau-, g̑hau̯ə-, pp. 413–414 or ĝheu-, pp. 447–448.]